Self-righting vessels for use with liquids are known in the art. For example, U.S. Pat. No. 4,953,737 ('737) describes the physics of self-righting behavior for his drinking cup for liquids having a lid for use by adults riding in a vehicle or a child in a highchair. The cup of the '737 patent neither rocks because of a round or hemispherical bottom nor relies on a weighted base. The inventor asserts that the self-righting capability is imparted to the vessel by the shape of the vessel sides, whose vertical cross section is an involute defined by a hypothetical circle located inside the cup. (See Column 1 lines 1-65) There is no indication that this invention would be suitable for granular solids or without a lid.
Another self-righting drinking cup is disclosed in U.S. Pat. No. 4,388,996, which also has a lid with a drinking spout. While a weight is shown in the bottom of the vessel, the inventor asserted that “Advantageously, since the cup has a high D/H ratio, it has a significant self-righting tendency without any weighting, and, as shown in FIG. 3, only a small weight is required to be added to assure consistent righting of the cup when filled or only partially filled, in resulting in a lightweight cup, e.g., weighing less than 15 grams per fluid ounce of cup capacity.
U.S. Pat. No. 434,423 discloses a self-righting milk bucket having a spherical bottom with a weight C, a safety tube D and a strainer G inside of the safety tube and generally coaxial therewith. The upper portion of the vessel is cone-shaped. The inventor asserts that: “If the upper portion of the bucket were not cone-shaped the bucket would not work in the manner heretofore described as the weight to the contained liquid would not be greatest at the bottom. It is essential that the great body of the milk, and hence the greatest weight, should be at the bottom to assist the return of the bucket to its normal position when tilted” (Column 2, lines 54-62).
Another example of a self-righting cup for liquids is shown in U.S. Pat. No. 2,601,767. It employs a lid or splash shield, which is readily inserted and removed from the cup opening to prevent large quantities of liquid spilling out of the cup when it is tipped over. Additionally, the lid is inwardly concave so that liquid spilling from what the inventor terms a recess 10 during use will be retained in the convexity and flow back to the cup through an opening and vent hole, 9 at the bottom-most portion of the lid. The cup has a false bottom 4 and a convex bottom 3 filled with shot for weight.
Animal and pet feeders are shown in U.S. Pat. Nos. 4,440,111 ('111) and 6,112,698 ('698). The '111 patent shows a cattle feeder with a hood 16. This is shown for cattle. Horse will not stick his head into a hood such as 16. Moreover, this patent shows a hemispherical base with, sand filling the base. A pan is inserted into the top of the base, which carries the feed supplement. The inventor says the hood is affixed to the base above the pan to protect the mineral supplement in the pan from the weather.
The '698 patent shows an ordinary pet bowl having inner and outer shells crimped together at their rims. The cavity between the shells is filled with sand as ballast to prevent the pet from tipping over the bowl. There are no arcuate side walls, the internal food cavity is straight-walled and there is no assertion that the bowl is self-righting.